WO-A-02070629 describes a process to prepare a gas oil product and a base oil product from a Fischer-Tropsch derived synthesis product by performing a hydroconversion/hydroisomerisation step and isolation of a gas oil fraction and a residue from the obtained cracked effluent. The gas oil as obtained had an iso-paraffin content of 80 wt %. The residue is further distilled to obtain a distillate fraction boiling between 370 and 510° C. This fraction boiling between 370 and 510° C. was subjected to a catalytic dewaxing step to obtain various base oil grades.
The present invention provides a process to optimise the yield to base oils from a Fischer-Tropsch derived synthesis product.